For controlling and if necessary regulating the combustion features during combustion processes there is a demand for a detection of at least one dimension for the particle concentration in the exhaust gas. There is especially a demand for detecting at least one dimension for the particle concentration in the exhaust gas of combustion engines, specifically of diesel combustion engines.
The term particle concentration equally faces a particle mass or a particle amount in the following. It will be referred to a particle mass only. The particle mass related to the time can be of interest. As long as the combustion process occurs in a combustion engine, which is arranged in a motor vehicle, the particle mass, which has accrued on a specific route, can be of interest.
In DE 101 33 285 A1 a particle sensor is described that contains a collecting chamber, which can be exposed to an off-gas stream. A first electrode is arranged on the top of the collecting chamber. A second electrode is arranged on the bottom, oppositely of the first electrode. The collecting chamber is hollow between both electrodes. During the operation of the sensor particles, especially soot particles, get into the collecting chamber and embed in the hollow between the two electrodes. The particles that are at least slightly electrically conductive bridge the gap between the two electrodes, so that the impedance of the sensor route of the particle sensor changes. The impedance or the timely change of the impedance, which are a measurement for the loading or the increase of the loading of the particle sensor with particles, can be evaluated. Since the measuring effect is based on an accumulation of particles, the particles sensor can be referred to as a collecting particle sensor.
In DE 101 33 384 A1 a further particle sensor described, at which the two electrodes intertwine comb-like. The impedance and/or the change between the two electrodes can also be used for this collecting particle sensor at least as a measurement for the particle mass in the exhaust gas, which occurred in a preset time and/or based on a route.
On the basis of experiments it turned out that the known collecting particle sensors, for example resistive particle sensors, show cross sensitivities, which can lead to an influencing of the measuring signal at a change of the conditions of the combustion process. Furthermore it turned out that the sensitivity of the particle sensor can be influenced by different substances in such a way that the sensitivity decreases towards the particles that have to be measured.
The invention is based on the assignment to provide a procedure for operating a particle sensor and a device for implementing this procedure, at which the measuring signal reflects a measurement as accurate as possible during the entire operating time for the particles that have to be detected.
This assignment is solved by the characteristics that are listed in the independent claims.